Method of forming electrical heat units.



R. W. DAVENPORT. METHOD OF FORIVHNG ELECTRICAL HEAT UNITS. APPLICATIONFILED APR.8.1Q15.

1 ,21 9,629. Patented Mar. 20, 1917.

UNITED STATES PATENT OFFICE.

RANSOM W. DAVENPORT, OF DETROIT, MICHIGAN, ASSIGNOR TO DETROIT STOVEWORKS 0F DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN.

METHOD OF FORMING ELECTRICAL HEAT UNITS.

Specification of Letters Patent Patented Mar. 20, 1917.

Griglnal application filed February 13, 1914, Serial No. 818,469.Divided and this application filed April 8,

To all whom it may concern:

Be it known that I, Ri-xNsoM V. DAVEN- ron'r, a citizen of the UnitedStates of America, residing at Detroit, in the county of Jayne and Stateor Michigan, have invent ed certain new and useful Improvements inMethods of Forming Flectrical Heating Units, of which the following is aspecification, reference being bad therein to the 1C- companyingdrawings The invention relates to the method. of forming electricalheating units of the embedded. resistor type, and it is the object ofthe invention to facilitate the embedding of the resistor, and also toobtain a construction in which there is good thermal conduction from theresistor on. one sic e and thermal insulation upon the opposite side. Itis a further object to obtain. a constructi n in which the convelutionsof the resistor are but slightly separated from each other, toconcentrate the heat development without any danger of short circuitingbetween convolntions,

An electrical heating unit of the embedded resistor type is disclosedin. my earlier application, Serial No. 818,469, filed Feb. 13, 1914:,the present application being a division thereof.

In the drawings:

Figure 'l is an elevation showing the method of coiling the resistor;

Fi 9 is a perspective View oi the coiled resistor;

Fig. 3 is a section showing the manner of engaging the resistorwith theheat-insulating body;

Fig. 4 is a similar View showing the spat?- ing member removed; and

Fig. is a cross section through the completed unit. I

In the first step oi my improved method 0.5 forming heating" units, theresistor A, which is pre'leral'ily in the form of a flat ribbon, isplaced adjacent to a destruetible strip or ribbon C, such as string,cord, twine, e c., and is then bent or fashioned to have adjacentcontacting portions. As specifically shown in Fig. 1, the bending is ina volute form, the convolutions of the re sister being: separated bythe. parallel conrelations of the destructible strip. After the ceilingthe convolutions are held from separation by suitable means such asbinding Serial No. 20,611.

strips D, and are preferably dipped in some adhesive, such as shellac.

The second step is the covering of the coil with a plastic material,which preferably a material of relatively low thermal conductivity, anexample of this material being infusorial silica with clay added forplasticity. The destructible strip is preferably slightly less in widththan the resistor, and therefore the. plastic material will slightlyenter in between the resistor convolutions to obtain a binding effectthereon.

The third step is the removal of the destructible strip, preferably bycombustion, after which the ashes are cleared away, prefcrably byblowing. This leaves the spaced conrolutions of the resistor, which areheld by the slight embedding 0t tl eir edges in the insulating material.

The next step is in filling the interstices or spaces between theresistor coni'olutions with a plastic material of relatively goodthermal coii(liicti\-'it y, an example of this material being calcinedbauxite or aluminum oxid with clay added for plasticity, and tlimaterial is extended a sullicient depth to form theheat distributingbody.

The unit when completed as described will have the maximum portion ofthe surface of the resistor convolutions in contact with a goodheat-conducting material. which will rapidly conduct the heat into thedistributing body. At the same time the h mt insulating body, which isupon the opposite side of the resistor, will prevent loss of h at \inthis direction, and as both or" the bodies are united to each other, theresistor will be completely embedded and thoroughly insulatedelectrically.

The destructible spacer strip which is wound between the resistorcmivolutions is preferably a round cord, which will leave. sulticientspace at the edge of the resistor for binding engagement of the plasticmaterial.

lVhat I claim as my invention is:-

l. The method of forming electrical heatinn elements, comprisinc theplacing oi a resistor strip and av strip formed of destructible materialadjacent to each other, bending said strips to form adjacent con tactingportions, placing plistic' material on one side in binding contact withthe resistor, and destroying the destructible element.

2. The method of forming electrical heating elements, comprising theplacing of a resistor ribbon and a destructible strip in parallelism,bending said parallel strips to form contacting adjacent portions,covering an area, placing plastic material of an electrically insulatingcharacter on one side in binding contact with the edges of the resistor,and destroying The method of forming electrical heatinc elements.comprising coiling an electrical resisto' and a parallel spacing stripto cover an area. placing plastic material on one side of said area intobinding contact with the edge of the resistor, and removing the spacingstrip.

4. The method of forming electrical heatin;- elements, comprising windinc together into a volute coil a length of resistor and an adjacentlength of destructible strip, cement ion a plate of insulating materialto one lace of said \olute coil iirbiliding contact with the edge of theresistor, and in burning out said destructiblc strip.

5. The method of forming electrical heating elements, comprising windingtogether a resistor and a parallel destructible spacer strip to term aclose coil, cementing a plate of insulating material upon one side 01said coil. destro \'ing the spacer strip and removing the same, andfilling the spaces vacated by said dcstructible strip with anelectrically insulating refractory material.

(3. The method 01 forming electrical heating elements, comprising thewinding together ot a resistor ribbon and a destructible spacer strip toform a close coil, cementing a plastic material of low thermalconductivity upon one side of said coil, destroying said spacing strip,and placing; a plastic material of relatively high thermal conductivityupon the opposite side of the coil and filling; the interstices betweenthe convolutions.

7. The method of forming electrical heating elements, comprising thewinding of a resistor and a destructible spacing strip into a volutecoil, coating one side of this coil with a plastic material, destroyingthe spacthe destructible strip.

ing strip and removing the same from the conyolutions of the resistor,and coating the opposite side of said resistor with a plastic material.5:

8. The method of forming electrical heating units, comprising thewinding of a resistor element and a parallel dcstrnctible spacing stripinto a yolute coil, binding the convolutions together to temporarilyhold the same in fixed relation, placing a plastic material on one sideof the coil and forcing the same sufficiently into engagement with thecmn'olutions of the resistor to bind the same in fixed relation,destroying the spacjug strip and removing" the same from between theresistor convolutions, and filling the space. between said convolutionsand upon the opposite face of the coil with a plastic material.

9. The method of forming electrical heating elements, comprising thewinding; of a resistor ribbon and a parallel strip of destructiblcmaterial into a rolute coil, coating;- one side of said coil with aplastic material of low thermoconductivity and forcing the samesutliciently in engagement with the convolntions of the resistor to bindthe same, destroying the spacing strip and removing it from between theresistor convolutions, and filling the space between said convolntionsand upon the opposite side of the coil with a plastic material ofrelatively high theri'no-condnctivity.

10. The method of forming electrical heating elements. comprising thewinding of a resistor and a spacing strip into a volnte coil, coatingone side of this coil with a plastic material, removing the strip frombetween the convolutions of the resistor, and

filling the interstices between the convohr tions with anelectrical-insulating, heatconducting material.

In testimony whereof I r 1n presence of two witnesses.

RANSOM lV. DAVENPORT. Witnesses lVM. J. BELKNAP, JAMES P. BARRY.

\' my signature

